Impulsive behavior is an important contributor to substance misuse, which is prevalent in college samples. Our center (CDART) has identified four distinct personality traits that underlie impulsive behaviors: Negative Urgency (NU), lack of Premeditation (PRE), lack of Perseverance (PSV) and Sensation Seeking (SS). Our previous work clarified the roles of SS and PRE in substance misuse in the college population. In our more recent work, NU has emerged as an important and independent contributor to substance misuse. Even after controlling for SS and PRE, NU is related to the onset and escalation of substance misuse and other risky behaviors, and the relation between NU and alcohol use is mediated through different mechanisms than the relations for PRE and SS. Thus, our previous work clearly shows that understanding NU is critically Important to the prevention of substance misuse in college populations. The four proposed studies will use a range of methods to investigate the nature of NU and the mechanisms through which it exerts its effects. Study 1 will identify underlying biological substrates of NU using fMRI. It is predicted that regions in the prefrontal cortex associated with inhibitory control will show less activation in high NU participants when participants are experiencing negative affect. Study 2 will identify the affective contexts and response characteristics most important to NU. It is predicted that affect will be more important to NU than to other impulsivity traits and that NU will manifest in impulsive behavior on tasks that include prepotent responses and/or tasks in which an impulsive response is negatively reinforced. Study 3 will examine the interactions among impulsivity traits, affective contexts, and interpersonal contexts in predicting impulsive behavior in daily life. It is predicted that NU will be related to impulsive behavior when high NU participants are under the influence of negative mood. Other impulsivity traits, like SS, may be more responsive to interpersonal contexts. Study 4 will test whether an intervention designed to help high NU participants respond more adaptively to their negative affect can reduce future impulsive behavior. It is predicted that mindfulness training will reduce impulsive behaviors among high NU individuals but not among high SS individuals. RELEVANCE (See instructions): Prevention of substance misuse in college samples is important because of the associated public health risks, including death, injury, long-term illness, and disability. Negative urgency is a strong but understudied predictor of substance misuse. The proposed studies will contribute to prevention research by clarifying the nature of negative urgency and the mechanisms through which it exerts its effects on substance misuse.